Objective Under the background of global climate change, ecosystems in high-altitude regions are becoming increasingly fragile and sensitive to both natural and anthropogenic disturbances. Railway construction, as a major form of infrastructure development, further intensifies ecological stress in these areas. The Lhasa–Linzhi Railway, located on the Qinghai-Xizang Plateau, passes through zones characterized by extreme environmental conditions, including low temperatures, strong radiation, and poor soil development. Shrub-herb communities in this region play a critical role in maintaining ecological stability, conserving soil and water, and supporting regional biodiversity. However, these communities are easily disturbed and difficult to restore once degraded. Therefore, this study aims to investigate the altitudinal distribution patterns and diversity characteristics of shrub-herb communities along the Lhasa–Linzhi Railway corridor, thereby providing a scientific basis for ecological restoration and soil and water conservation in high-altitude railway ecosystems.

Methods The study was conducted along the Lhasa–Linzhi Railway corridor, where ten representative sample plots were established across an altitudinal gradient ranging from 3 000 m to 3 900 m. Field surveys were carried out during the peak growing season to ensure accurate observation of vegetation conditions. Within each plot, detailed vegetation investigations were performed to record species composition, floristic characteristics, plant cover, height, and community structure. Species richness and abundance data were systematically collected. To quantitatively evaluate biodiversity, multiple α-diversity indices were calculated, including the Shannon-Wiener index, Simpson index, and Pielou’s evenness index, which reflected species diversity, dominance, and distribution uniformity. In addition, β-diversity indices such as the Cody index and Sørensen index were used to assess species turnover and community differentiation along the altitudinal gradient. The Jaccard similarity coefficient was also applied to evaluate the similarity of species composition among different plots at varying altitudes.

Results The results revealed several significant patterns in the shrub-herb communities along the Lhasa–Linzhi Railway. 1) In terms of floristic composition, the communities were dominated by cosmopolitan and North Temperate distribution types, indicating a strong influence of temperate elements. Endemic species were present but accounted for a relatively small proportion, suggesting that harsh environmental conditions limited local specialization. 2) α-diversity exhibited a clear unimodal pattern along the altitudinal gradient. Species richness, diversity, and evenness all reached their peak at mid-altitudes, particularly between 3 300 m and 3 500 m, where environmental conditions such as temperature and moisture were relatively favorable. In contrast, at higher altitudes, communities became increasingly simplified, with fewer species and lower evenness, as extreme environmental factors restricted species survival and distribution. 3) β-diversity increased with increasing altitudinal difference. As the altitude difference between sample plots widened, community similarity decreased significantly, and species turnover became more pronounced, indicating strong environmental filtering effects along the gradient.

Conclusions Altitudinal gradient is a key factor influencing the structure, composition, and diversity of shrub-herb communities along the Lhasa–Linzhi Railway corridor. The observed unimodal pattern of α-diversity and the increasing trend of β-diversity highlight the importance of environmental gradients in shaping community dynamics. These findings indicate that ecological restoration strategies in high-altitude railway regions should fully consider altitudinal variation. Restoration efforts should prioritize mid-altitude zones with higher biodiversity potential while adopting adaptive and site-specific measures for high-altitude areas with harsher conditions. Overall, this study provides important scientific support for optimizing vegetation restoration strategies and implementing effective soil and water conservation practices in fragile alpine ecosystems.